<!-- If this is set, it adds or subtracks from any conditions that require a relationship to last for X rounds -->
<property name="Relationships Last Extra Rounds" value="0" editable="true">
<number min="-1" max="2"/>
</property>

Typically relationships last 1 round and utilize endRound delegate to determine when that is. But the condition option (conditionAttachment option) for custom diplomacy is below.

relationship values: a relationship that needs to be present in the game: "player1:player2:relationship" (will set #rounds to -1 by default) OR "player1:player2:relationship:numberOfRoundsThisRelationshipMustExistForMinimum" for example: "Japan:China:War" or "Japan:China:War:-1" or "Japan:China:War:3". It will accept "anyWar", "anyNeutral" and "anyAllied" as well.

Some games use multi rounds relationships. They probably use the simple game property "relationship last extra rounds" to just add on versus creating new political actions using the condition ^^.

Note the condition would likely be used to activate triggerAttachment option, such as below.

relationshipChange values: the change in relationship for these players, format: "player1:player2:oldRelation:newRelation" example: "Russians:Americans:coldWar:allOutWar" oldRelation may be "any", "anyWar", "anyNeutral", "anyAllied", or an actual relationshipType used in this xml. You can enter multiple relationshipChanges in the trigger and it will perform every change in the trigger which is valid.